1. Field of the Invention
The present invention generally relates to an apparatus for manufacturing tonyu and tofu. In particular, it is concerned with an apparatus that can perform at least part of the entire manufacturing process automatically and consecutively needing only a single equipment.
Definition of the terms
Throughout this specification and the appended claims, the terms peculiar to the art to which this invention belongs are used in accordance with the definitions given in the following brief description of tonyu and tofu manufacturing process.
In general, tofu (beancurd) has conventionally been produced in a process comprising the following successive steps: namely, the first step of soaking soybeans in water to swell soybeans sufficiently, the second step of smashing or grinding the swollen soybean to debris to obtain raw gojiru (crude slurry of the debris suspended in water), the third step of boiling the raw gojiru to give cooked gojiru, whereby soy protein and any other water-soluble or emulsifiable components are extracted, the fourth step of separating the cooked gojiru into tonyu (soybean juice) and okara (bean cakes or beancurd refuses, insoluble or non-emulsifiable components of soybean), the fifth step of coagulating the separated tonyu by adding coagulating agent and the sixth step of molding the tonyu to give tofu while the tonyu is coagulating.
2. Description of Prior Art
The apparatus shown in FIG. 5 is an example of the known tonyu making apparata.
As shown in FIG. 5, a lower body 1 houses an electric motor 2, and an upper body 3 is mounted detachably on the lower body 1. A mixercup 5 having plural water expelling openings 4 at its upper part is placed in the upper body 3. A bearing 6, which rotatably supports an axle 7, is provided in the mixercup 5 at the center of its bottom plate. The lower end of the axle 7 is adapted to engage with a driving shaft 8 of the electric motor 2 and a mixer cutter 9 is provided on the upper end of the axle 7.
The relationship between the rotating axle 7 and the mixercup 5 is such that; a tubular body 10 extends downwardly from the bottom plate of the mixercup 5 to envelop the rotating axle 7 with an annular cylindrical space, which houses a coil spring 11 for exhibiting a resistance against the rotating movement of the rotating axle 7 only in one rotating direction. In that arrangement, the mixercup 5 will not be driven by the rotating axle 7 while it is rotating in one direction at a high number of revolution. Conversely, the mixercup 5 is driven to rotate by the axle 7 with an adequate friction of a contacting component such as coil spring 11 while the axle 7 is rotating in the reverse direction at a low number of revolution.
In addition, an outlet 12 for tonyu is provided in the lower part of the upper body 3 whose top end is covered with a lid 13 with a heater 14 for heating the contents of the mixercup 5. A timer 15 is provided for contorolling the successive steps of the process.
In the known tonyu making apparatus constructed as illustrated above, the mixer cutter 9 starts to smash the soybean at its high speed rotation when the mixercup 5 is filled with the soybean and the corresponding amount of water and covered with the lid 13, and the timer 15 is set. After smashing for a predetermined time period, the electric motor 2 stops and current is supplied to the heater 14 to boil the smashed contents.
After the end of the boiling, the supply of current to the heater stops and simultaneously the electric motor 2 starts to rotate at a lower rotational frequency in the reverse direction. In this time however, the mixercup 5 starts to be driven to rotate integrally with the axle 7 by the binding action of the coil spring 11. Then, the mixercup 5 serves as a separating container for expelling tonyu which has been produced by extracting water-soluble or emulsifiable components of soybean debris during the boiling step from the outlets 12, while retaining the separated okara (beancurd refuses) in the mixercup 5.
In the step of smashing soybean in the above process, a clearance between the mixercup 5 and the mixer cutter 9 is required to be minimized in order to ensure an effective smashing operation. On the other hand, the mixercup 5 has to be tall with respect to its diameter if it should be filled with water of the amount sufficient for the manufacture of tonyu. Such a tall shape of the mixercup 5 may frequently cause vibration at the step of centrifugal dewatering. In addition, a deep mixercup is usually hard to clean after use. The cleaning operation will become more troublesome if ribs or blades for effective collision of the soybeans with the mixer cutter and preventing revolution of the material are provided on the inner side wall of the mixercup 5. Furthermore, the ribs may exclude provision of a filter on the inner side wall of the mixercup 5 and result in very poor separation of tonyu from okara (beancurd refuses).
Moreover, when the mixer cutter 9 rotates at high rotational frequency to smash the soybeans, the mixercup 5 tends to be driven undesirably causing centrifugal dewatering during the smashing operation, thereby deteriorating the smashing performance. If the heating time at the boiling step is regulated only by the timer 15, boiling of the contents may be insufficient or excessive because the temperature of tap water may differ depending on seasons. Thus, a sensor for accurately sensing the temperature of the content should be provided to adjust the extent of boiling. However, the provision of the temperature sensor in an appropriate position is not always possible if the mixercup 5 is designed to rotate.
Furthermore, the downwardly extending structure of the heater to be immersed in the contents may also be troublesome in its handling and disadvantageous in view of sanitary conditions and even heating of the contents.